Dig Energy has completed its first commercial project: seven geothermal boreholes drilled at the Boston headquarters of general contractor Suffolk Construction. The startup claims its purpose-built rig can cut drilling costs by up to 80% compared with conventional geothermal equipment — a claim now backed, at least directionally, by its first jobsite performance.

The company emerged publicly roughly a year ago, announcing a $5 million funding round after about five years of development work conducted in a barn in New Hampshire. At the same time, Dig joined Boost, an accelerator run by Suffolk Technologies, the venture capital affiliate of Suffolk Construction — the relationship that produced the inaugural project.

The technical problem Dig targets is straightforward. Geothermal heating and cooling, which pairs all-electric heat pumps with underground thermal storage, is widely regarded as the most efficient way to condition buildings. But installation costs can run up to five times those of an equivalent air-source heat pump, and only about 1% of U.S. buildings use geothermal systems, according to Dig co-founder and CEO Dulcie Madden.

How the rig works

Conventional geothermal drilling bores the hole first with a metal bit or compressor, installs casing to prevent collapse, and then inserts a heat exchange pipe. Dig's system replaces the mechanical bit with a high-pressure nozzle spraying water at 10,000 pounds per square inch to cut through soil and rock. The oil and gas industry explored the approach decades ago but abandoned it because it did not improve productivity in those sectors, Madden said. She and her partners adapted it for geothermal.

"It's a known industry practice that's being adopted in a novel way for the first time," Madden said.

The second design decision matters as much as the jetting. Dig engineered the drill string — the vertical components connecting surface equipment to the drill tip — to remain in the ground after drilling, becoming the heat exchanger itself. The nozzle also stays downhole; the company designed it to be cheap enough to sacrifice on every hole.

Because no casing is needed and no separate heat exchanger is inserted after the fact, the borehole can have a smaller diameter than in conventional systems. That reduces debris and, counterintuitively, water consumption: standard drilling uses large volumes of water to lubricate and cool bits and to convert displaced earth into removable mud.

Jobsite numbers

At the Boston site last month, the rig used one-tenth the water conventional drilling would have required and generated 75% less material to haul away, Madden said. The operation was also dramatically quieter — standard drilling, in Madden's comparison, resembles a demolition site. Workers could hold a conversation next to Dig's rig, and people in nearby buildings heard nothing.

The rig's footprint, roughly that of a parking spot per Suffolk Technologies partner Parker Mundt, made it maneuverable in a dense urban environment.

"You can have people working around the rig without any disruption," Mundt said.

Dig and Suffolk declined to disclose specific cost figures for the project. But Dig "put some early proof points out there that, from a cost and schedule perspective, they're going to be very competitive in the market," Mundt said.

What comes next

The order book is the clearest signal. Dig has several more jobs lined up and is booked until mid-summer 2027, according to Madden. The company is also developing a new version of the rig designed to shorten drilling time.

"The results from this initial commercial project at our headquarters were incredibly exciting for us," Mundt said.

For now, Dig's cost-reduction claim rests on a seven-borehole sample and unaudited jobsite metrics. What decides whether the 80% figure holds is scale: whether the second-generation rig sustains the water and spoil reductions across dozens of commercial sites, and whether published per-borehole pricing follows. The backlog through mid-2027 gives the company the runway to prove both.